arduino-TuyaOpen: Off-by-one Error
CVE-2026-28520 is a high-severity off-by-one error vulnerability in arduino-TuyaOpen from Tuya, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists version 1.2.1 as the first without the flaw, so updating arduino-TuyaOpen to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.21% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update arduino-TuyaOpen to 1.2.1 or a later version.
- Read the advisory on src.tuya.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Tuya | arduino-TuyaOpen | before 1.2.1 | 1.2.1 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.6 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 8.4 | High | CNA (vulncheck.com) |
Official description
arduino-TuyaOpen before version 1.2.1 contains a single-byte buffer overflow vulnerability in the WiFiMulti component. When the victim's smart hardware connects to an attacker-controlled AP hotspot, the attacker can exploit the overflow to execute arbitrary code on the affected embedded device.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Off-by-one Error
A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
How developers prevent this class of flaw
- When copying character arrays or using character manipulation methods, the correct size parameter must be used to account for the null terminator that needs to be added at the end of the array. Some examples of functions susceptible to this weakness in C include strcpy(), strncpy(), strcat(), strncat(), printf(), sprintf(), scanf() and sscanf().
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
Other references
Other vulnerabilities in arduino-TuyaOpen
- 7.7 High severity
- 8.8 High severity
Recent Off-by-one Error vulnerabilities
- 7.5 High severity
- 9.8 Critical severity
- 10.0 Critical severity
- 7.8 High severity
- 7.5 High severity
- 7.1 High severity
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